Effects of temperature on the reproductive life history of the black vine weevil, Otiorhynchus sulcatus

Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae) is one of the most serious pests of horticultural crops but despite this, the effects of temperature on its reproduction are not fully understood. This study investigates the effects of temperature on the full set of reproductive traits of O. sulcatus at nine temperatures between 11 and 36 degreesC and develops descriptive models for each trait. Cohorts of newly eclosed adults were subjected to these temperatures and fed on Rhododendron spec. leaves. Adults oviposited at temperatures from 11 to 27 degreesC. Significant differences among treatments were found in the preoviposition period, oviposition period, longevity, per capita egg production, and egg viability. The preoviposition period was the shortest at 24 degreesC and the longest at 11 degreesC. With a non-linear model fitted to the data across the full range of experimental temperatures, the lower and upper threshold temperatures and optimum temperature for reproductive maturation were estimated to be 6.8, 30.0, and 22.7 degreesC, respectively. The developmental threshold and calculated thermal constant were estimated to be 6.7 degreesC and 505.0 degree-days, respectively, using a linear model at temperatures between 11 and 21 degreesC. Maximum per capita egg production (1094.1 eggs) and highest egg viability (90.1%) were both observed at 21 degreesC. The median longevity of O. sulcatus adults in the 18-36 degreesC range decreased linearly as temperatures increased. At 27 degreesC or above, the reproductive success of O. sulcatus was substantially impaired, and the optimum temperature range was 21-22 degreesC. Production of viable eggs in relation to temperature and weevil age was simulated by incorporating four models of life history traits, including egg production, egg viability, cumulative pattern of egg production, and adult survival. Overall, the present study demonstrates that temperature is a key factor in determining the reproductive success of O. sulcatus adults. We hypothesize that temperature may influence the phenology and geographic distribution of O. sulcatus populations.